Sensor device and method

ABSTRACT

A sensor device and method. One embodiment provides a first semiconductor chip having a sensing region. A porous structure element is attached to the first semiconductor chip. A first region of the porous structure element faces the sensing region of the first semiconductor chip. An encapsulation material partially encapsulates the first semiconductor chip and the porous structure element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Utility Patent Application is a divisional application of U.S.application Ser. No. 12/402,912, filed Mar. 12, 2009, which isincorporated herein by reference.

BACKGROUND

This invention relates to an electronic device including a sensor and amethod of manufacturing thereof.

In the development of devices including sensors special requirements maybe taken into account, in particular when designing the package of asensor device. For example, certain sensors, such as pressure sensors,gas sensors or humidity sensors, may require an opening through whichthe fluid which is to be detected is applied to the sensor.

For these and other reasons there is a need for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1 schematically illustrates one embodiment of a sensor deviceincluding a semiconductor chip having a sensing region, a porousstructure element and an encapsulation material.

FIG. 2 schematically illustrates one embodiment of a sensor deviceincluding a semiconductor chip having a sensing region, a structureelement and a carrier.

FIGS. 3A to 3C schematically illustrate one embodiment of a method tomanufacture a sensor device.

FIG. 4 schematically illustrates one embodiment of a sensor deviceincluding a first semiconductor chip having a sensing region, a porousstructure element and a second semiconductor chip.

FIG. 5 schematically illustrates one embodiment of a semiconductor chiphaving a sensing region arranged between two substrates.

FIG. 6 schematically illustrates one embodiment of a sensor deviceincluding a first semiconductor chip having a sensing region, astructure element having an inlet and an outlet and a secondsemiconductor chip.

FIG. 7 schematically illustrates one embodiment of a sensor deviceincluding a first semiconductor chip having a sensing region, astructure element having multiple inlets and an outlet and a secondsemiconductor chip.

FIG. 8 schematically illustrates one embodiment of a sensor deviceincluding a first semiconductor chip having a sensing region, an o-ringand a second semiconductor chip.

FIG. 9 schematically illustrates one embodiment of a device including asensor device.

FIGS. 10A to 10G schematically illustrate one embodiment of a method tomanufacture a sensor device including a semiconductor chip having asensing region, a porous structure element and an encapsulationmaterial.

FIG. 11 schematically illustrates one embodiment of a plasma jetgenerator.

FIG. 12 schematically illustrates one embodiment of a sensor deviceincluding a semiconductor chip having a sensing region, a porousstructure element and a leadframe.

FIG. 13 schematically illustrates one embodiment of a sensor deviceincluding a semiconductor chip having a sensing region and a porousleadframe.

FIG. 14 schematically illustrates one embodiment of a sensor deviceincluding a semiconductor chip having a sensing region and a circuitboard having a porous region.

FIG. 15 schematically illustrates one embodiment of a sensor deviceincluding a semiconductor chip having a sensing region and a circuitboard having a porous region.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

It is to be understood that the features of the various exemplaryembodiments described herein may be combined with each other, unlessspecifically noted otherwise.

As employed in this Specification, the terms “coupled” and/or“electrically coupled” are not meant to mean that the elements must bedirectly coupled together; intervening elements may be provided betweenthe “coupled” or “electrically coupled” elements.

Devices containing sensors are described below. A sensor measures (orsenses) a physical variable, such as for example pressure, temperature,occurrence and/or quantity of a substance, magnetic field, humidityetc., and converts the measured variable to a signal which can be readby an observer or an instrument. Examples of sensors are pressuresensors, tire pressure sensors, gas sensors and humidity sensors.Sensors may include a sensing region which allow to measure the desiredvariable. In the case of a pressure sensor, the sensor surface may be asurface of a membrane which is used for measuring the pressure of afluid, such as a gas or a liquid. Other examples of a sensing region area cantilever, a bridge, a gas sensing surface and a tongue structure.The sensors may be configured as MEMS (micro-electro mechanical systems)and may include micro-mechanical structures, such as bridges, membranesor tongue structures.

The sensors may be integrated in semiconductor chips. Furthermore, thesensor devices described below may contain one or more additionalsemiconductor chips which do not contain sensors. The semiconductorchips may be of different types, may be manufactured by differenttechnologies and may include for example integrated electrical,electro-optical or electro-mechanical circuits or passives. Theintegrated circuits may, for example, be designed as logic integratedcircuits, analog integrated circuits, mixed signal integrated circuits,power integrated circuits, memory circuits or integrated passives. Thesemiconductor chips may be configured as antennas and/or discretepassives and/or chip stacks. Semiconductor chips in which suchfunctional elements are embedded generally contain electronic circuitswhich serve for driving the functional elements or further processingsignals generated by the functional elements. The semiconductor chipsneed not be manufactured from specific semiconductor material, forexample Si, SiC, SiGe, GaAs, and, furthermore, may contain inorganicand/or organic materials that are not semiconductors, such as forexample discrete passives, antennas, insulators, plastics or metals.Moreover, the semiconductor chips may be packaged or unpackaged.

The semiconductor chips may have contact pads (or electrodes) whichallow electrical contact to be made with the integrated circuitsincluded in the semiconductor chips. One or more metal layers may beapplied to the contact pads of the semiconductor chips. The metal layersmay be manufactured with any desired geometric shape and any desiredmaterial composition. The metal layers may, for example, be in the formof a layer covering an area. Any desired metal or metal alloy, forexample aluminum, titanium, gold, silver, copper, palladium, platinum,nickel, chromium or nickel vanadium, may be used as the material. Themetal layers need not be homogenous or manufactured from just onematerial, that is to say various compositions and concentrations of thematerials contained in the metal layers are possible. The contact padsmay be situated on the active main faces of the semiconductor chips oron other faces of the semiconductor chips.

The sensor devices described below include external contact elements orexternal contact pads, which may be of any shape and size. The externalcontact elements may be accessible from outside the sensor device andmay thus allow electrical contact to be made with the semiconductorchips from outside the sensor device. Furthermore, the external contactelements may be thermally conductive and may serve as heat sinks fordissipating the heat generated by the semiconductor chips. The externalcontact elements may be composed of any desired electrically conductivematerial, for example of a metal, such as copper, aluminum or gold, ametal alloy or an electrically conductive organic material. Soldermaterial, such as solder balls or solder bumps, may be deposited on theexternal contact elements.

The semiconductor chips containing the sensors may be attached to porousstructure elements. The porous structure elements may be made of a solidmaterial permeated by an interconnected network of pores (voids). Theinterconnected network of pores may allow fluid flow through thestructure element. Although the porous structure element may cover thesemiconductor chip and in particular the sensing region of thesemiconductor chip, the sensing region may be in fluid connection withthe outside of the sensor device. Thus the fluid (gas or liquid) to bedetected may permeate through the porous structure element to thesensing region of the semiconductor chip. The diameter of the pores ofthe porous structure element may be in the range from 10 nm to 500 μmand in particular in the range from 0.5 μm to 200 μm. The pores may beuniformly or non-uniformly distributed over the porous structureelement. Porous material of which the porous structure element may bemade are, for example, glass frit, ceramic frit, porous adhesivematerial, aerogel and porous metal. An example of porous metal is castiron. The porous structure element may be made of one piece and may nothave additional channels or openings which are larger than the pores ofthe porous structure element.

The structure element may also be made of a non-porous material whichdoes not allow fluid flow through this material. In this case one ormore channels may be introduced into the structure element. Thestructure element may have at least one inlet at its outside surface andat least one outlet next to the sensing region of the semiconductorchip. The inlets and outlets may be in fluid connection by using thechannels through the structure element. The non-porous structure elementmay be made of glass, ceramics, plastics or any other appropriatematerial.

The semiconductor chips or at least parts of the semiconductor chips maybe covered with an encapsulation material, which may be electricallyinsulating. The encapsulation material may be any appropriate laminate(prepreg) or thermoplastic or thermosetting material. The encapsulationmaterial may, for example, be a mold material which may be based on anepoxy material and may contain a filling material consisting of smallparticles of glass (SiO₂) or other electrically insulating mineralfiller materials like Al₂O₃ or organic filler materials. Varioustechniques may be employed to cover the semiconductor chips with themold material, for example compression molding, injection molding,powder molding, liquid molding and transfer molding.

The sensors, which may be integrated in semiconductor chips, as well asfurther semiconductor chips may be placed on carriers. The carriers maybe of any shape, size or material. During the fabrication of the devicesthe carriers may be connected to each other. The carriers may also bemade from one piece. The carriers may be connected among each other byconnection means with the purpose of separating the carriers in thecourse of the fabrication. Separation of the carriers may be carried outby mechanical sawing, a laser beam, cutting, stamping, milling, etchingor any other appropriate method. The carriers may be electricallyconductive. They may be fabricated from metals or metal alloys, inparticular copper, copper alloys, iron nickel, aluminum, aluminumalloys, or other appropriate materials. The carriers may be, forexample, a leadframe or a part of a leadframe. Furthermore, the carriersmay be plated with an electrically conductive material, for examplecopper, silver, iron nickel or nickel phosphorus.

FIG. 1 schematically illustrates a sensor device 100 in cross section.The sensor device 100 includes a first semiconductor chip 10 having asensing region 11, a porous structure element 12 and an encapsulationmaterial 13. The porous structure element 12 is attached to the firstsemiconductor chip 10 with a first region 14 of the porous structureelement 12 facing the sensing region 11 of the first semiconductor chip10. The encapsulation material 13 encapsulates the first semiconductorchip 10 and the porous structure element 12 only partially.

The encapsulation material 13 may encapsulate the porous structureelement 12 such that a second region 15 of the porous structure element12 may be exposed from the encapsulation material 13 and may be incontact with the outside environment a parameter of which is to bedetected by the sensor device 100. The first region 14 of the porousstructure element 12 may be in fluid connection with the second region15 of the porous structure element 12. Due to this fluid connection, thesensing region 11 of the first semiconductor chip 10 may be in fluidconnection with the outside environment.

FIG. 2 schematically illustrates a sensor device 200 in cross section.The sensor device 200 includes a first semiconductor chip 10 having asensing region 11, a structure element 12 and a carrier 16. Thestructure element 12 may be stacked on the carrier 16, and the firstsemiconductor chip 10 may be stacked on the structure element 12. Thestructure element 12 may have an inlet 17 and an outlet 18. The outlet18 may be in fluid connection with the inlet 17 and the sensing region11 of the first semiconductor chip 10. This may allow the sensing region11 of the first semiconductor chip 10 to be in fluid connection with theenvironment outside of the sensor device 200.

The carrier 16 may, for example, be a second semiconductor chip or aleadframe or any other substrate.

FIGS. 3A to 3C schematically illustrate a method for manufacturing asensor device 300, which is illustrated in cross section in FIG. 3C.Firstly, a first semiconductor chip 10 having a sensing region 11 isprovided (see FIG. 3A). The first semiconductor chip 10 is attached to aporous structure element 12 such that the sensing region 11 faces afirst region 14 of the porous structure element 12 (see FIG. 3B). Thefirst semiconductor chip 10 and the porous structure element 12 areencapsulated such that a second region 15 of the porous structureelement 12 remains exposed. An encapsulation material 13, for example amold material or a laminate, may be used to encapsulate the firstsemiconductor chip 10 and the porous structure element 12. The firstregion 14 of the porous structure element 12 may be in fluid connectionwith the second region 15 of the porous structure element 12.

FIG. 4 schematically illustrates a sensor device 400 in cross section(top) and along a line A-A′ (bottom). The sensor device 400 is animplementation of the sensor device 100 shown in FIG. 1. The details ofthe sensor device 400 that are described below can therefore be likewiseapplied to the sensor device 100.

In one embodiment, the sensor device 400 includes a pressure sensor. Thepressure sensor is integrated in the first semiconductor chip 10. Moredetails of the first semiconductor chip 10 are schematically illustratedin FIG. 5. The first semiconductor chip 10 may contain a silicon body20, which may be manufactured of p-type doped silicon, and a membrane21, which may be manufactured of n-type doped silicon. The membrane 21is arranged over a recess (opening) 22 formed in the silicon body 20.The recess 22 exposes the sensing region 11 of the first semiconductorchip 10, which is the lower surface of the membrane 21 exposed by therecess 22.

When integrated in the sensor device 400, the first semiconductor chip10 may be placed on a substrate 23. Furthermore, a substrate 24 may bestacked on top of the first semiconductor chip 10. Both substrates 23and 24 may be manufactured of glass, silicon or another appropriatematerial. The substrates 23 and 24 may have been attached to the firstsemiconductor chip 10 when the first semiconductor chip 10 was still inthe wafer bond. The substrates 23 and 24 may have been attached to thesemiconductor wafer by anodic bonding and thereafter the semiconductorwafer may have been diced thereby separating the individual firstsemiconductor chips 10. The substrate 23 has a through-hole 25 in thearea of the recess 22, and the substrate 24 has a recess 26 over themembrane 21. The recess 26 in the substrate 24 forms a sealed cavityover the membrane 21. This cavity may be filled with a gas at areference pressure. The deflection of the membrane 21 which is due todifferent pressures on both sides of the membrane 21 is a measure of thepressure to be sensed.

There are two main types of pressure sensor, resistive and capacitive.Both types of theses sensors rely on the deflection of the membrane 21under an applied pressure difference. The resistive-type pressure sensormay employ a number of piezoresistors 27 on one face of the membrane 21.Two of these piezoresistors 27 are illustrated in FIG. 5. Thepiezoresistors 27 are electrically coupled to contact pads 28 of thefirst semiconductor chip 10 by using conductor tracks 29. The firstsemiconductor chip 10 may include any number of contact pads 28, inFIGS. 4 and 5 only one of the contact pads 28 is illustrated. Theconductor tracks 29 may be made of any appropriate metal or metal alloy,for example aluminum or copper. The conductor tracks 29 are arrangedbetween electrically insulating layers 30 and 31, which may for examplebe made of silicon nitride, photoresist or any other appropriateelectrically insulating material.

The substrate 23 may be stacked on top of the porous structure element12. The porous structure element 12 may be made of a solid materialpermeated by an interconnected network of pores (voids). Theinterconnected network of pores may allow fluid flow through thestructure element 12. Although the porous structure element 12 maycompletely cover the through-hole 25 in the substrate 23, the sensingregion 11 of the membrane 21 may be in fluid connection with the outsideof the sensor device 400 due to the porosity of the porous structureelement 12. This is because at least one or more side walls 15 of theporous structure element 12 may be exposed to the outer environment.Thus the fluid to be detected, which may be a gas or liquid, maypermeate through the porous structure element 12 to the membrane 21.

The pores of the porous structure element 12 may not all have the samediameter. The diameters of the pores may be distributed over a certainrange. For example, the diameters of the pores of the porous structureelement 12 may be in the range from 10 nm to 500 μm and in particular inthe range from 0.5 μm to 200 μm. In particular, the diameters of thepores may be smaller than 500 μm, 400 μm, 300 μm, 200 μm, 100 μm, 50 μm,10 μm or 1 μm. The pores may be uniformly or non-uniformly distributedover the porous structure element 12. Porous material of which theporous structure element 12 may be made are, for example, glass frit,ceramic frit, porous adhesive material, aerogel and porous metal. Anexample of porous metal is cast iron. The porous structure element 12may be made of one piece and may not have additional channels oropenings which are larger than the pores of the porous structure element12. The height h₁ of the porous structure element 12 may be greater than20 μm.

The surface of the porous structure element 12 which faces the substrate23 may be larger than or equal to or smaller than the surface of thesubstrate 23 facing the porous structure element 12.

The porous structure element 12 may be stacked on a second semiconductorchip 16, which may be an ASIC (Application Specific Integrated Circuit).The second semiconductor chip 16 may have one or more contact pads 32.The contact pads 32 may, for example, be located on the upper surface ofthe second semiconductor chip 16. One of the contact pads 32 isexemplarily shown in FIG. 4. Some of the contact pads 32 of the secondsemiconductor chips 16 may be electrically coupled to the contact pads28 of the first semiconductor chip 10, for example by using bond wires33.

The function of the second semiconductor chip 16 may be to control thefirst semiconductor chip 10 and/or to record the sensor signals obtainedfrom the sensor of the first semiconductor chip 10 and to process and/orevaluate the sensor signals. The arrangement of the porous structureelement 12 between the first and second semiconductor chips 10 and 16allows the recess 22 in the first semiconductor chip 10 and thethrough-hole 25 in the substrate 23 to face towards the secondsemiconductor chip 16. Due to the porosity of the porous structureelement 12 it is still possible that the membrane 21 is in fluidconnection with the environment outside the sensor device 400.

FIG. 6 schematically illustrates a sensor device 600 in cross section(top) and along a line A-A′ (bottom). The sensor device 600 is animplementation of the sensor device 200 shown in FIG. 2. The details ofthe sensor device 600 that are described below can therefore be likewiseapplied to the sensor device 200.

The sensor device 600 is almost identical to the sensor device 400. Theonly difference between the sensor devices 400 and 600 is the structureelement 12 arranged between the first semiconductor chip 10 and thesecond semiconductor chip 16. The structure element 12 of the sensordevice 600 is made of a non-porous material. In general, this materialdoes not allow fluid flow through the material. In order to have a fluidconnection between the environment outside the device 600 and thesensing region 11 of the first semiconductor chip 10, a channel 40 hasbeen introduced into the structure element 12. The channel 40 may havean inlet 17 at one of the side surfaces of the structure element 12 andan outlet on the upper surface of the structure element 12 next to thesensing region 11 of the first semiconductor chip 10. The inlet 17 andthe outlet 18 may be in fluid connection by using the channel 40 throughthe structure element 12. The channel 40 may be of any shape and mayhave a minimum diameter of at least 100 μm, 300 μm, 500 μm, 600 μm, 700μm, 800 μm, 900 μm or 1 mm. The structure element 12 may be made of anysuitable material, for example glass, ceramics or plastics.

In one embodiment, the structure element 12 has more than just onechannel 40. Such a sensor device 700 is schematically illustrated inFIG. 7. The sensor device 700 has four channels 40 and each of thechannels 40 leads to a respective one of the side surfaces of thestructure element 12. Furthermore, the structure element 12 may have anynumber of channels and any number of inlets and outlets.

In one embodiment, which is schematically illustrated in FIG. 8, asensor device 800 includes an o-ring as the structure element 12. Theo-ring 12 misses at least one section which allows fluid flow from theoutside of the sensor device 800 to the sensing region 11 of the firstsemiconductor chip 10. The o-ring 12 may be made of any appropriatematerial, for example glass, silicone, polymers, plastics or ceramics.

It is obvious to a person skilled in the art that the devices 100 to 800described above and illustrated in FIGS. 1 to 8 are only intended to beexemplary embodiments, and many variations are possible. For example,additional semiconductor chips or passives of different types may beincluded in the same device. The semiconductor chips and passives maydiffer in function, size, manufacturing technology etc.

Instead of a pressure sensor, other kinds of sensors may be integratedin the sensor devices 100 to 800, for example gas or humidity sensors.In case the first semiconductor chip 10 includes a gas sensor, thesensing region 11 of the first semiconductor chip 10 may be afunctionalized surface. If this surface is exposed to a gas, specificgas molecules adsorb onto the functionalized surface, thereby changingthe electrical conductivity of the sensing surface. This change inelectrical conductivity may be measured in order to determine theoccurrence of the desired gas and/or its proportion in the gas beinganalyzed.

In order to avoid humidity or water to penetrate the structure element12 and to impair the function of the sensor devices 100 to 800, theouter surface of the structure element 12 or the entire surface of thestructure element 12 may be coated with an hydrophobic layer. Forexample, polytetrafluoroethylene (commercially available under thetradename Teflon) or other fluor-containing organic polymers may bedeposited on the surface of the structure element 12. In one embodiment,the devices 100 to 800 may contain a heating element, for example aresistor or a conductor loop, in order to heat the structure element 12to keep it free of humidity or water. In one embodiment, the pores ofthe porous structure element 12 may be small enough that the coating ofthe fluor-containing organic polymers has a hydrophilic effect so thatthe sensor devices 100 to 800 may function as humidity sensors.

The devices 100 to 800 may also be integrated in other devices. Anexample of such a device 900 is schematically illustrated in FIG. 9 incross section. The device 900 may contain a circuit board 50, which maybe a PCB (Printed Circuit Board). The circuit board 50 may includecontact pads 51 on its upper surface and external contact pads 52 on itslower surface. Furthermore, the circuit board 52 may contain one or morewiring layers 53 to electrically couple the contact pads 51, 52 witheach other. Some of the contact pads 51, 52 and the wiring layers 53 areexemplarily illustrated in FIG. 9. Solder deposits 54 may be depositedon the external contact pads 52.

The sensor device 400 may be attached to the upper surface of thecircuit board 50. The second semiconductor chip 16 may be electricallycoupled to the contact pads 51 of the circuit board 50 and othersemiconductor chips by bond wires 55 or other appropriate connectionsmeans. Moreover, a semiconductor chip 56 may be mounted on the circuitboard 50 in a flip-chip manner, and a semiconductor chip 57 may bestacked on the semiconductor chip 56. A housing 58 having a through-hole59 may protect the semiconductor chips and devices mounted on thecircuit board 50.

In one embodiment, the device 900 may be a tire pressure sensor. Thesensor device 400 may be embodied as a pressure sensor, thesemiconductor chip 56 may include a radio transceiver, and thesemiconductor chip 57 may include a BAW (Bulk Acoustic Wave) filter.

FIGS. 10A to 10G schematically illustrate a method for manufacturing asensor device 1000, a cross section of which is illustrated in FIG. 10G.The sensor device 1000 is one implementation of the sensor devices 100to 800. The details of the sensor device 1000 that are described belowcan therefore be likewise applied to the sensor devices 100 to 800.Furthermore, the method illustrated in FIGS. 10A to 10G is animplementation of the method illustrated in FIGS. 3A to 3C. The detailsof the production method that are described below can therefore belikewise applied to the method of FIGS. 3A to 3C.

In order to manufacture the device 1000, a leadframe 60 may be providedwhich is illustrated in FIG. 10A in cross section. The leadframe 60 mayinclude one or more die pads 61 and a plurality of leads 62. Theleadframe 60 may be manufactured from a metal or metal alloy, inparticular copper, a copper alloy, iron nickel, aluminum, or otherappropriate materials. Furthermore, the leadframe 60 may be plated withan electrically conductive material, for example copper, silver, ironnickel or nickel phosphorus. The shape of the leadframe 60 is notlimited to any size or geometric shape. The leadframe 60 may have beenmanufactured by punching a metal plate. The die pads 61 and leads 62 ofthe leadframe 60 may be connected to each other by dams (not shown inFIG. 10A).

As illustrated in FIG. 10B, the second semiconductor chip 16 is placedover the die pad 61. In the present embodiment, the second semiconductorchip 16 is mounted on the die pad 61 with the contact pads 32 facingaway from the die pad 61. The second semiconductor chip 16 may beattached to the die pad 61 by using an appropriate adhesive material.

As illustrated in FIG. 10C, the porous structure element 12 is mountedon the upper surface of the second semiconductor chip 16 using anappropriate adhesive material, for example glue. In the presentembodiment, the porous structure element 12 protrudes over at least oneside surface of the second semiconductor chip 16. The porous structureelement 12 may have been separated from a larger piece of porousmaterial, for example by cutting, sawing, etching or laser ablation.

As illustrated in FIG. 10D, the stack including the substrate 23, thefirst semiconductor chip 10 and the substrate 24 may be mounted on theupper surface of the porous structure element 12 using an appropriateadhesive material, for example glue. The substrate 23 may be placed overthe porous structure element 12 such that the through-hole 25 in thesubstrate 23 is completely covered by the porous structure element 12.

Additional semiconductor chips and/or components may be placed over thedie pad 61. Furthermore, the leadframe 60 may contain further die pads,which are not illustrated in FIGS. 10A to 10G and on which furthersemiconductor chips and/or components may be placed.

Electrical interconnections may be established between the contact pads28 and 32 of the semiconductor chips 10 and 16 and the leads 62 of theleadframe 60. Two examples of these interconnections are illustrated inFIG. 10E where the interconnections are made by wire bonding. The bondwire 33 connects one of the contact pads 28 with one of the contact pads32, and the bond wire 63 connects one of the contact pads 32 with one ofthe leads 62. For example, ball bonding or wedge bonding may be used asthe interconnect technique. The bond wires 33, 63 may be made up ofgold, aluminum, copper or any other appropriate electrically conductivematerial.

Instead of wire bonding, other interconnect techniques may be used. Forexample, metallic clips may be placed on the semiconductor chips 10 and16 as well as the leads 62 or flip-chip bonding may be used to establishthe electrical interconnections.

A mold transfer process may be carried out to encapsulate the componentsarranged on the leadframe 60 with a mold material (encapsulationmaterial) 13 as illustrated in FIG. 10F. The mold material 13 mayencapsulate any portion of the device 1000, but leaves at least thesecond region 15 of the porous structure element 12 uncovered. In oneembodiment, the second region 15 of the porous structure element 12includes at least a side surface of the porous structure element 12. Thesecond region 15 of the porous structure element 12 is in fluidconnection with the first region 14 of the porous structure element 12.Due to this fluid connection, the sensing region 11 of the firstsemiconductor chip 10 is in fluid connection with the outsideenvironment.

Moreover, some parts of the leads 62 are not covered with the moldmaterial 13. The exposed parts of the leads 62 may be used as externalcontact elements to electrically couple the device 1000 to othercomponents, for example a circuit board, such as a PCB.

In order to apply the mold material 13 to the components arranged on theleadframe 60, the leadframe 60 may be placed in a mold form or moldcavity (not illustrated in FIG. 10F). The mold cavity is a hollowed-outblock that is filled with the mold material 13 after placing theleadframe 60 in the mold cavity. After the mold material 13 has hardenedinside the mold cavity, the mold material 13 adopts the shape of themold cavity.

The mold material 13 may be composed of any appropriate electricallyinsulating thermoplastic or thermosetting material, in one embodiment itmay be composed of a material commonly used in contemporarysemiconductor packaging technology. The mold material 13 may be based onan epoxy material and may contain a filling material consisting of smallparticles of glass (SiO₂) or other electrically insulating mineralfiller materials like Al₂O₃ or organic filler materials. Varioustechniques may be employed to cover the components of the device 1000with the mold material 13, for example compression molding, injectionmolding, powder molding, liquid molding and transfer molding.

Before or after the encapsulation with the mold material 13, theindividual devices 1000 are separated from one another by separation ofthe leadframe 60, for example by sawing or cutting the dams. Asillustrated in FIG. 10G the leads 62 may be bent and/or trimmed in orderto mount the device 1000 on a circuit board. Instead of having the leads62 protruding from the mold material 13, it is also possible to have aleadless device 1000.

For the purpose of a corrosion prevention the devices 100 to 1000 may becoated with a layer of Si_(x)O_(y)C_(z), wherein the x, y and z may beintegers or fractions. The layer of Si_(x)O_(y)C_(z) may be deposited byusing an atmospheric pressure plasma jet generator 70 as schematicallyillustrated in FIG. 11. The plasma jet generator 70 has a pot-shapedhousing 71 with a lateral connection 72 to the supply line for a workinggas. A nozzle pipe 73 is held inside the housing 71 in a coaxialposition. A pin electrode 74 is centered inside the housing 71. Theouter circumference of the nozzle pipe 73 is covered by a jacket 75 madeof electrically conductive material forming a ring electrode 76 at theunattached front or lower end of the nozzle pipe 73. A high frequencygenerator 77 applies an alternating current between the ring electrode76 and the pin electrode 74. The connection 72 for the working gas isinstalled such that the supplied working gas spins helically as it flowsthrough the nozzle pipe 73 as indicated by the helical arrow 78 in FIG.11. When an appropriate voltage is applied between the pin electrode 74and the ring electrode 76, a corona discharge takes place at the tip ofthe pin electrode 74. This corona discharge provides the necessary ionsto strike an arc discharge 79 from the pin electrode 74 to the ringelectrode 76 when the voltage is increased. The arc discharge 79produces a plasma jet 80 which is used for the treatment of the surfacesof the devices 100 to 1000.

Volatile organic silicon compounds, for example tetraethoxysilane(TEOS), may be supplied to the connection 72 as a working gas. Theplasma converts the organic silicon compounds to high reactive chemicalmolecule fragments. These molecule fragments are transported to thesurfaces of the devices 100 to 1000 where they polymerize toSi_(x)O_(y)C_(z). The thickness of the layers produced by this methodmay be smaller than 5 μm.

A sensor device 1200 according to one embodiment is schematicallyillustrated in FIG. 12 in cross section. The sensor device 1200 isidentical to the sensor device 1000 illustrated in FIG. 10G in manyways. In contrast to the sensor device 1000, the sensor device 1200 doesnot contain the second semiconductor chip 16, but the porous structureelement 12 is directly attached to the die pad 61. Furthermore, at leasttwo side surfaces of the porous structure element 12 are exposed fromthe mold material 13 in the sensor device 1200.

A sensor device 1300 according to one embodiment is schematicallyillustrated in FIG. 13 in cross section. In contrast to the sensordevice 1200, the substrate 23 of the sensor device 1300 is directlyplaced onto the die pad 61 and the leadframe 60 is made of a porousmetal, for example cast iron. The die pad 61 and at least one lead 90are made in one piece so that the die pad 61 and the lead 90 have thesame function as the porous structure element 12 of sensor device 1200.

A sensor device 1400 according to one embodiment is schematicallyillustrated in FIG. 14 in cross section. In the sensor device 1400 thestack consisting of the substrate 23, the first semiconductor chip 10and the substrate 24 is mounted on a circuit board 91. The porousstructure element 12 is integrated such into the circuit board 91 thatit covers the through-hole 25 in the substrate 23 and the lower surfaceof the porous structure element 12 is exposed. Thus, in this embodiment,the second region 15 is the lower surface of the porous structureelement 12. Moreover, a housing 92 is placed over the stack consistingof the substrate 23, the first semiconductor chip 10 and the substrate24 as well as the bond wires 33 coupling the first semiconductor chip 10to the circuit board 91.

A sensor device 1500 according to one embodiment is schematicallyillustrated in FIG. 15 in cross section. The sensor device 1500 isalmost identical to the sensor device 1400, however the shape of theporous structure element 12 is different. In the sensor device 1500 theporous structure element 12 is shaped such that the exposed secondregion 15 of the porous structure element 12 is located on the uppersurface of the circuit board 91.

In addition, while a particular feature or aspect of an embodiment ofthe invention may have been disclosed with respect to only one ofseveral implementations, such feature or aspect may be combined with oneor more other features or aspects of the other implementations as may bedesired and advantageous for any given or particular application.Furthermore, to the extent that the terms “include”, “have”, “with”, orother variants thereof are used in either the detailed description orthe claims, such terms are intended to be inclusive in a manner similarto the term “comprise”. Furthermore, it should be understood thatembodiments may be implemented in discrete circuits, partiallyintegrated circuits or fully integrated circuits or programming means.Also, the term “exemplary” is merely meant as an example, rather thanthe best or optimal. It is also to be appreciated that features and/orelements depicted herein are illustrated with particular dimensionsrelative to one another for purposes of simplicity and ease ofunderstanding, and that actual dimensions may differ substantially fromthat illustrated herein.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

1. A sensor device, comprising: a first semiconductor chip having asensing region; a carrier; and a structure element arranged between thefirst semiconductor chip and the carrier, the structure element havingan inlet and an outlet, the outlet being in fluid connection with theinlet and the sensing region.
 2. The sensor device of claim 1,comprising wherein the structure element is a porous structure elementcomprising pores having diameters smaller than 500 μm.
 3. The sensordevice of claim 1, comprising wherein the carrier is a secondsemiconductor chip and at least one bond wire electrically couples thefirst semiconductor chip to the second semiconductor chip.
 4. The sensordevice of claim 3, comprising wherein the at least one bond wire iscoated with silicon oxide.
 5. The sensor device of claim 1, furthercomprising: a housing in which the first semiconductor chip, the carrierand the structure element are placed.
 6. The sensor device of claim 1,comprising wherein the sensor device is at least one of a pressuresensor, a tire pressure sensor, a gas sensor and a humidity sensor.
 7. Amethod of manufacturing a sensor device, comprising: providing a firstsemiconductor chip having a sensing region; attaching the firstsemiconductor chip to a porous structure element with the sensing regionfacing a first region of the porous structure element; and encapsulatingthe first semiconductor chip and the porous structure element such thata second region of the porous structure element remains exposed.
 8. Themethod of claim 7, comprising wherein the first region of the porousstructure element is in fluid connection with the second region of theporous structure element.
 9. The method of claim 7, wherein the porousstructure element comprises pores having diameters smaller than 500 μm.10. The method of claim 7, comprising attaching the porous structureelement to a second semiconductor chip.
 11. The method of claim 10,comprising stacking the porous structure element onto the secondsemiconductor chip and stacking the first semiconductor chip onto theporous structure element.
 12. The method of claim 7, comprisingattaching at least one of the first semiconductor chip, the secondsemiconductor chip and the structure element to a carrier.
 13. Themethod of claim 7, wherein encapsulating the first semiconductor chipand the porous structure element comprises placing the firstsemiconductor chip and the porous structure element is a mold form. 14.The method of claim 7, comprising depositing a layer of silicon oxideonto the sensor device using a plasma deposition method.